The present invention relates to a probe assembly for monitoring the water level in boilers fitted with an electric immersion resistor heater.
This type of probe assembly can be applied to boilers of electrical household appliances, industrial machines, boilers for domestic heating, et cetera.
In these applications it is possible to restore the level of the water inside the boiler on the basis of the indication of one or more probes that enter said boiler and monitor said level.
However, prior probes are not free from drawbacks.
The main one is the fact that the probes are exposed to the turbulence that is normally present inside the boiler chamber, consequently altering the sensitivity of the probe or probes.
The variation of the sensitivity of the probe or probes causes it or them to emit signals indicating that the lower limit of the water level has been reached at incorrect times and in incorrect manners.
In particular, the greatest damage occurs when the probe is late in detecting that the lower limit of the water level has been reached and therefore it is necessary to add substantial amounts of cold water in order to restore the optimum level; the injection of cold water lowers the internal temperature of the boiler, consequently lowering the pressure.
This pressure drop accordingly causes a delay in the supply of steam, which in the case of electric household appliances leads to an idle time during cleaning operations.
Furthermore, it has been noted, especially after long and prolonged use, that the probes currently in use tend to fill with scale, causing new problems in addition to the ones already described in relation to turbulence.
In order to solve the above cited drawbacks, solutions have been proposed in which the probe or probes are inserted in hollow bodies for protection against turbulences.
Although these solutions are effective, they have nonetheless not solved other drawbacks related to the positioning of the electrical connections of the probes as well as to the possibility of accidental opening of the closure plug.
The electrical connection cable is in fact currently rigidly coupled to the top of the plug and this entails that in order to comply with currently applicable safety standards it is necessary to cover said cable with a door (for example, one cannot leave an external cable, since it could be pulled and might break), with consequent constructive complications and limitations.
The aim of the present invention is to provide a probe assembly for monitoring the water level in boilers provided with an electric immersion resistor heater which solves the above mentioned drawbacks of prior models, particularly providing an optimum positioning of the electrical connections of the probe or probes and at the same time ensuring a detection that is always effective and accurate even in the presence of high turbulence inside the boiler and of scale deposits on said probes.
Within this aim, an important object of the present invention is to provide a probe assembly that complies with safety standards and therefore has a high level of safety for the user and for the operator, preventing accidental and/or inadvertent openings of the closure plug, as well as pulling of the electrical connection wire.
Another object of the present invention is to provide a probe assembly whose application does not detract in any way from the performance of the boiler.
Another object of the present invention is to provide a probe assembly with high flexibility of application in relation to the type of boiler and its intended use.
Another object of the present invention is to provide a probe assembly that can be manufactured with known technologies and systems and at prices that are competitive with respect to competing commercially available probe assemblies.
This aim and these and other objects that will become better apparent hereinafter are achieved by a probe assembly for monitoring the water level in boilers with an electric immersion resistor heater, of the type that comprises at least one sensor element to be arranged inside a hollow body which is in turn associated and partially inserted in the boiler, said assembly being characterized in that said hollow body has, on the portion arranged outside the boiler, a plug which axially supports said sensor element, the end of said sensor element arranged at said plug being connected, when said plug is installed, by means of at least one electrical contact, to an electrical power supply cable, whose contact end is arranged at said portion of hollow body that is arranged outside the boiler.